A police officer could be blinded after a full bottle of lager was smashed in his face during a street attack.

A mindless thug launched the Stella bottle at the bobby with such force that it smashed on impact.

Specialists at the University Hospital of Wales carried out emergency surgery to save the eye but it is not yet clear how much sight the 31-year-old, from Cardiff, will have.

Police and union leaders have condemned the attack on the off-duty officer who was returning home from a meal with his girlfriend and her cousin.

Detective Constable Steve Colston said: 'These were three innocent people who were walking back from the pub having enjoyed a quiet meal when they were set upon by a gang of youths.

'One of the youths, without provocation, caused horrific injuries potentially threatening his livelihood. Two 16-year-old males from the Thornhill area have been released on bail.'

The appalling attack happened just before 1am on Saturday close to the junction of Cavendish Close and Brookvale Drive, in Thornhill, Cardiff, when the group were followed by a gang of between five and eight youths. They shouted abuse at the off-duty Gwent police officer who was then pushed and punched a couple of times to the head.

DC Colston said: 'One of the group took a Stella bottle and threw it into the side of his face. It smashed on impact causing severe damage to his eye.

'Surgery to save his eye has been successful but they can't say whether he will have sight out of it.'

The Caerphilly-based Pc, who has four years service didn't identify himself as a police officer until the end of the attack and it is not thought he was targeted because of his profession.

Secretary of the Gwent Police Federation Peter Anderson said: 'We certainly wish him well and he has our full support to ensure he returns, as far as possible, to full duty.'

Anyone with information is asked to contact Dc Colston at Llanedeyrn CID on 029 2052 7444 or Crimestoppers anonymously on 0800 555 111.